The present invention relates to gate valves and, more particularly, to gate valves having replaceable one piece molded liners.
Generally, a gate valve body is machined from a single piece casting. The chest and seat of the body are machined to receive a gate. The gate is milled with parallel opposed faces in close conformity with the valve body chest. Gate valves of this type must generally be replaced in toto after a period of use dependent upon the type and consistency of the fluid flowing through the gate valve. Such replacement is expensive.
In order to overcome the expenses attendant replacement of complete gate valves, various gate valves have been developed which incorporate individually replaceable chests, collars,, backing strips and seats. U.S. Pat. No. 3,624,882 is representative of gate valves of this type. Herein, segregated elements forming the seat and seals are separately replaceable. U.S. Pat. No. 3,194,259, describes a gate valve having a replaceable unitary structure defining segregable and distinct elements such as the gate, gate housing, seats and gate actuating mechanisms, which structure is disposed within the gate valve body. U.S. Pat. No. 3,521,667, discloses a yet further type of control valve wherein a seat element and supporting structure is readily replaceable as a unit.
In all the known prior art gate valves, the gates are machined to have parallel opposed surfaces in order to provide a good seal and smooth operation. The requirement for such machining tends to preclude the gates from being interchangeable and necessitates that the gates be custom fitted to the gate valve bodies and necessarily increases the cost of the available gate valves.
It is therefore a primary object of the present invention to provide a gate valve with a replaceable one piece liner which defines the chest and seat for the gate.
Another object of the present invention is to provide a one piece bore and chest liner for receiving the gate of a gate valve which both seats and seals the gate.
Yet another object of the present invention is to provide a removable gate seat for gate valves.
Still another object of the present invention is to provide a low cost gate valve body and liner.
A further object of the present invention is to provide a low cost cast gate for use with a one piece liner in gate valves.
A yet further object of the present invention is to provide a gate valve having low maintenance costs.
A still further object of the present invention is to provide a one piece liner for gate valves which eliminates the need for gaskets intermediate attached piping.
A still further object of the present invention is to provide a gate valve constructable from a wide range of metallic and nonmetallic materials, the selection of which material is primarily dependent upon the nature of the fluid flowing through the valve and without negatively affecting the operation of the valve.
These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds.